This study examines the item and dimension distribution and factorial reliability and validity of the GM@W questionnaire for assessing the 13 dimensions of the work environment outlined in The Canadian National Standard for Psychological Health and Safety in the Workplace (The Standard). Methods An internet survey of 1,006 Ontario workers was conducted between February 10th and March 5th, 2020. Respondents had to be employed in a workplace with five or more employees. The survey included the 65 items from the GM@W questionnaire, and questions to assess sociodemographic characteristics and employment arrangements. Analyses examined the distribution of scores for items and for overall dimensions. A confirmatory factor analysis (CFA) examined the relationship between the 13 proposed dimensions and each of the 65 questions, using only respondents with complete information (N = 900). Results Low levels of missing responses were observed, although 14 of the 65 items had potential ceiling effects. CFA analyses demonstrated poor fit for the conceptual model linking the 13 dimensions of The Standard to the 65-items. High correlations between dimensions were also noted. The GM@W questionnaire displayed poor discriminant in measuring the specific dimensions proposed in The Standard. Conclusions Our results suggest the GM@W survey is unable to isolate the proposed dimensions of the psychosocial work environment as outlined in The Standard. These limitations are important, as workplaces using the GM@W survey will not be able to identify dimensions of the work environment which require attention or assess changes in particular dimensions over time.